1. Field of the Invention
The present invention relates to an endoscope cleaning sheath that sprays a fluid mixture in a spray state towards an observation window or the like of an endoscope to remove an adhering substance that is adhered to the observation window or the like, as well as an endoscope apparatus comprising the cleaning sheath.
2. Description of the Related Art
When in vivo mucus, blood, fat, dirt or the like adhere to an observation window, illumination window or the like comprised by an endoscope during observation using the endoscope, favorable observation is prevented.
Japanese Patent Laid-Open No. 2004-267583 (hereunder, referred to as Patent Document 1), for example, discloses a laparoscope defogging apparatus to solve the problems caused by such adherence. A laparoscope defogging apparatus is a separate device to a laparoscope, and is attached to a laparoscope to prevent fogging and the like of a distal end portion of the laparoscope. The laparoscope defogging apparatus illustrated in FIG. 4 of Patent Document 1 has a cylindrical body 3. The cylindrical body 3 has an opening 30 at the proximal end and an opening 31 at the distal end thereof. An optical transmission member 4 that has a hydrophilic coating formed thereon is provided on the side of the opening 31 of the cylindrical body 3. A main unit 1 of the laparoscope can be inserted from the opening 30 at the proximal end of the cylindrical body 3. The cylindrical body 3 comprises a light guide 35 for irradiating light from the distal end and a moisture supply hole 37 for supplying moisture. Accordingly, by supplying moisture to the optical transmission member 4 on which the hydrophilic coating is formed through the moisture supply hole 37 on the coating surface of the optical transmission member 4, the surface of the optical transmission member undergoes self cleaning.
In the above described laparoscope defogging apparatus, prevention of fogging that occurs on the surface of the optical transmission member 4 is effective in a case in which dirt such as blood is adhered in a very small quantity on the surface. However, once dirt such as blood has adhered to the surface of the optical transmission member 4, it is difficult to remove the adhering substance.
It is already known that spraying a fluid mixture of water and air in a spray state towards the external surface of an observation window from a spray nozzle produces a better cleaning effect than a case of spraying only water onto the surface of an observation window. Further, Japanese Patent Publication No. 63-49502 (hereunder, referred to as Patent Document 2) discloses an endoscope in which means that cleans an outer surface of an observation window is improved. Furthermore, Japanese Patent Laid-Open No. 2004-141367 (hereunder, referred to as Patent Document 3) discloses a water pipeline for an endoscope that ejects a fluid mixture of water and air in a spray state from the distal end of an insertion portion without swelling a patient's body cavity employing a simple configuration.
On an endoscope main unit 1 shown in FIG. 1 of Patent Document 2, a switching valve 16 is provided in an operation portion 2. Supply of a fluid mixture of a cleaning liquid and a gas and supply of only air can be selectively performed to a spray nozzle 6 when a supply hole 11 comprising an air supply channel 12 and a liquid supply channel 13 is switched by a changeover operation of the switching valve 16. The switching valve 16 is configured by inserting a piston 18 into a cylinder 17, and a throttle 29 that suppresses the amount of fed air when supplying a fluid mixture is formed as suppression means in the piston 18. As shown in FIG. 2 of Patent Document 2, when cleaning an observation window 5, a leak hole 27 of the piston 18 is blocked with a finger and the piston 18 is inserted. Subsequently, feeding of air that passes through the air supply channel 12 and feeding of liquid that passes through the liquid supply channel 13 are performed at the same time to mix the cleaning liquid and gas at a position immediately before the spray nozzle 6. By mixing the cleaning liquid and gas at a position immediately before the spray nozzle 6, a fluid mixture is sprayed in a spray state towards an observation window 5 from the spray nozzle 6 to remove dirt that is adhered to the surface of the observation window 5.
Accordingly, it is considered that dirt adhering to the optical transmission member 4 will be removed by supplying a fluid mixture to the moisture supply hole 37 of the laparoscope defogging apparatus, more specifically, by supplying a fluid mixture from a water supply hole 36.
A fluid ejection opening 6 aligned with an observation window 3 is formed on a distal end surface of a distal end portion main unit 2 of an insertion portion 1 illustrated in FIG. 1 of Patent Document 3. A water supply channel 7 is formed at the rear of the distal end portion main unit 2. A narrowed portion 7a that locally narrows the cross sectional area of the flow channel is formed at a portion towards the tip of the water supply channel 7. A distal end portion from the narrowed portion 7a to the fluid ejection opening 6 is formed in a shape that widens in a trumpet shape. A ventilation path 9 is formed in the distal end portion main unit 2. One end of the ventilation path 9a opens on a lateral wall surface near the outlet of the narrowed portion 7a of the water supply channel 7, and the other end opens towards the external surface on the distal end surface of the distal end portion main unit 2. According to this configuration, when water is fed to the water supply channel 7 through a water supply tube 8 and the water passes through the narrowed portion 7a, the flow rate of the water flow at that portion quickens and the pressure decreases. Thereupon, air in the area surrounding the distal end portion main unit 2 is sucked into the narrowed portion 7a through the ventilation path 9 and, as a result, a fluid mixture of water and air is ejected from the fluid ejection opening 6.